The present invention relates to electrical stimulating devices for application to the human body and, more particularly, to transcutaneous nerve stimulator systems for providing external electrical signals for body stimulation and treatment.
Transcutaneous nerve stimulating circuits are conventionally used in the prior art to provide patient treatment by applying electrical stimulation externally to the body for treatment of pain and muscular problems. The technique involves the application of electrical impulses to various parts of the body at different magnitudes and durations. The impulses are provided by conventional pulse-producing circuitry which produces pulses of various magnitudes and durations and a variety of timing intervals. The pulses are coupled through electrodes which are attached to the skin of a patient for coupling to the body.
While the application of the transcutaneous nerve stimulations has been a long-standing practice, and has appeared to provide various degrees of relief from pain and other muscle problems, the technique and the devices used to produce the electrical impulses pose a danger to an individual because of the electrical pulses being used. This danger is related to the normal heart function and beat pattern of the heart in the body. As is known, the typical heartbeat waveform is repetitive and consists of specific periods generally known as the P, Q, R, S, and T portions of the heartbeat. Each of the individual portions are known by the respective capital letters as the particular wave portion of the heartbeat. The time duration of each of the periods is generally well-known and the whole time period from the beginning of one heartbeat period to the beginning of the next heartbeat period is generally about 900 milliseconds. Of this 900 millisecond period, the T-wave portion lasts approximately 100 milliseconds and is considered the vulnerable period of the heartbeat.
The T-wave portion is considered the vulnerable period because of the tendency of the heat to go into ventricular fibrillation if it is electrically stimulated during that period. Ventriclar fibrillation is a state in which the heart does not beat properly and prevents proper operation of the heart valves to control blood flow through the body. When blood flow is lost, oxygen and other nutrients required by the heart and other portions of the body are not provided because of lack of blood flow, and serious injury can result. Because the heart is susceptible to electrical stimulation during the T-wave portion, it is necessary to take great care to prevent electrical stimulation to or around the heart during that time period.
During the use of transcutaneous nerve stimulators, the application of unwanted electrical signals can be prevented by localizing the treatment away from the heart. This technique still poses a problem, however, because of uncontrolled electrical paths during body stimulation. While the electrodes may be positioned to provide the stimulation to a particular area, some portion of the energy provided to the electrodes can be passed to other parts of the body where no stimulation is required or desired. If this were to happen to the heart during the T-wave portion of the heartbeat, the stimulation could cause the unnatural interruption of the heartbeat.
In the prior art, the problem has been reduced to some degree by reducing the magnitude of the nerve stimulation pulses below a level at which the heart would be disrupted if any electrical stimulation is received during the T-wave portion. In addition, the electrodes are usually applied to parts far from the heart to avoid inadvertent stimulation of the heart muscle. While this technique may be successful in eliminating most of the danger, it also reduces the effectiveness of transcutaneous nerve stimulation since greater magnitude pulses than safety dictates are required for the proper treatment of the body portions.
There is thus a need for a transcutaneous nerve stimulation system which will enable the application of greater magnitude pulses while reducing the danger of inadvertent electrical stimulation of the heart. The present invention has therefore been developed to overcome the shortcomings of the above known and similar systems and techniques and to provide a transcutaneous nerve stimulation and inhibiting system for inhibiting electrical signals during the T-wave portion of the heartbeat.